Structure for mounting fuel cock in motorcycle

ABSTRACT

A structural layout of a motorcycle concerning a fuel tank, a fuel cock, a carburetor, and an engine in relation to a frame is provided. A downward projecting portion is provided on a bottom of the fuel tank towards the rear. The projecting portion extends in a space defined behind a cylinder head and a cylinder head cover of the engine and in front of a rear cross member of the frame. The downward projection is juxtaposed with a carburetor across a motorcycle body. The fuel cock is manually accessible from beneath the one of right or left main frames of the frame.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a structure for mounting a fuelcock in a motorcycle.

[0003] 2. Description of the Relevant Art

[0004] Japanese Patent Publication No. Hei 8-5419 discloses amotorcycle, in which a fuel tank is supported on a pair of left andright main frames. The left and right mainframes extend above theengine, and along the length of the motorcycle. A recess is formed onthe lower side surface of the fuel tank. The fuel cock is provided inthe recess, and near the upper surface of the main frames.

[0005] In a design structuring of a motorcycle, a fuel tank should beprovided at a lower level, so that the center of gravity of themotorcycle is positioned as low as possible. However, the position ofthe fuel tank is dependent upon the height of a cylinder head of anengine, in order to supply fuel from the fuel tank to a carburetor usinggravity.

[0006] It may also be desirable to increase the capacity of the fueltank, however, if the fuel tank is made tall to increase its capacity, ariding position or a seat shape will be affected. Further, the center ofgravity of the motorcycle may vary extensively with an amount of fuelremaining in the fuel tank, or a rider's posture. Still further, whenthe fuel tank is positioned between the left and right main frames, itis difficult to attach a fuel cock at a position where it is easy toaccess and maintain.

SUMMARY OF THE INVENTION

[0007] It is an object of the present invention to overcome one or moreof the drawbacks of the background art.

[0008] In order to accomplish the above-mentioned objects of theinvention, there is provided a structure for mounting a fuel cock in amotorcycle in which a fuel tank is provided above an engine. A fuel cockand a carburetor are juxtaposed under a fuel tank and across amotorcycle body.

[0009] According to the invention, the fuel cock and the carburetor arejuxtaposed across the motorcycle body, so that the fuel cock can betheoretically positioned at a lowest level, and the fuel tank has itsrear part positioned under the center of the motorcycle body. Thisstructure allows a riding position and a seat to be secured near thefront part of the motorcycle body, increases the capacity of the fueltank, and contributes to stabilizing the center of gravity of themotorcycle. Further, both the fuel cock and the carburetor arejuxtaposed across the motorcycle body at the lower position thereof.This improves layout tolerance for the fuel cock. Still further, sincethe fuel cock is present at the lowest position of the fuel tank, littleair will be sucked from the fuel tank as a fuel level varies when thereis a small amount of fuel remaining in the fuel tank.

[0010] Other objects and further scope of applicability of the presentinvention will become apparent from the detailed description givenhereinafter. However, it should be understood that the detaileddescription and specific examples, while indicating preferredembodiments of the invention, are given by way of illustration only,since various changes and modifications within the spirit and scope ofthe invention will become apparent to those skilled in the art from thisdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus, are notlimitative of the present invention, and wherein:

[0012]FIG. 1 is a left side view of an off-road type motorcycle, inaccordance with the present invention;

[0013]FIG. 2 is a left side view illustrating an arrangement ofcomponents positioned above an engine of the motorcycle;

[0014]FIG. 3 is a plan view of the motorcycle, showing the layout of thecomponents shown in FIG. 2;

[0015]FIG. 4 is a left side view illustrating a layout of componentspositioned above pivot plates of a frame of the motorcycle;

[0016]FIG. 5 is a close-up view of the components around a down tube ofthe motorcycle's frame;

[0017]FIG. 6 illustrates a layout of components in a space under a rearcross member of the motorcycle's frame;

[0018]FIG. 7 is a left side view of several parts of the motorcycle'sframe;

[0019]FIG. 8 is a plan view of the front part of the motorcycle's frame;

[0020]FIG. 9 is a plan view of the rear part of the motorcycle's frame;and

[0021]FIG. 10 is a cross sectional view, taken along line 10-10, in FIG.7.

DETAILED DESCRIPTION OF THE INVENTION

[0022] Referring to FIG. 1, a motorcycle body frame 1 has a cradle shapeand supports a water-cooled 4-cycle engine 2. The motorcycle body frame1 includes a pair of left and right main frames 4. The left and rightmainframes 4 extend from a headpipe 3, over the engine 2, to the rear ofthe vehicle.

[0023] A down tube 5 is positioned in front of the engine 2, and extendsforward and downward from the head pipe 3 along the center of amotorcycle. A pair of left and right pivot plates 6 are coupled to rearends of the right and left main frames 4. The left and right pivotplates 6 extend upward and downward behind the engine 2.

[0024] A pair of left and right lower frames 7 extend under the engine 2and connect a lower end of the down tube 5 to the left and right pivotplates 6, respectively. A pair of seat rails 8 extend rearward fromupper ends of the pivot plates 6. The pair of seat rails 8 have theirrear ends connected to intermediate portions of the pivot frames 6 usingan oblique rear pipe 9.

[0025] Left and right front forks 11 are movably supported by the headpipe 3 via top and bottom bridges 12 and 13. The left and right frontforks 11 are steered by a handle bar 10. FIG. 1 also illustrates a frontwheel 14.

[0026] A front end of a rear swing arm 16 is movably supported at theintermediate portions of the pivot frames 6 using a pivot shaft 15. Arear wheel 17 is supported by the rear end of the rear swing arm 16. Arear shock absorber or strut 19 is attached between a link 18 in frontof the rear swing arm 16 and a rear cross member 43 at the upper ends ofthe pivot plates 6 (to be described later). The rear shock absorber orstrut 19 and its connections are part of a rear wheel suspension system.

[0027] A fuel tank 20 is supported between the left and right mainframes 4. A seat 21 is supported on the left and right seat rails 8.FIG. 1 also illustrates radiators 22, an exhaust pipe 23, a carburetor24, an air cleaner 25, and a muffler 26 of the motorcycle.

[0028] As shown in FIG. 2, the engine 2 is a water-cooled 4-cycleengine, including a cylinder head 27 standing substantially upright. Acylinder head cover 28 is substantially triangular, when viewed from theleft side of the motorcycle. The rear end of the cylinder head cover 28extends into a space between the right and left main frames 4. Anexhaust passage 35 is provided at the front center of the cylinder head27, and connects to the exhaust pipe 23.

[0029] As illustrated in FIG. 5, left and right radiators 22 aresupported at opposite sides of the down tube 5. A return water hose 31extends between upper tanks 30 of the radiators 22. A water hose 33extends between lower tanks 32 of the radiators 22, and is connected toa crankcase 29 (see FIG. 2).

[0030] As illustrated in FIG. 2, the carburetor 24 is connected to anintake port on the rear surface of the cylinder head 27. The carburetor24 has an intake upstream side thereof connected to a front part of theair cleaner 25 via a connecting tube 36. The connecting tube 36 extendsacross a part where the rear ends of the main frames 4 and the upperpart of the pivot plates 6 are joined, when viewed from the left side ofthe motorcycle.

[0031] The connecting tube 36 is divided at the center thereof into afront part 36 a and a rear part 36 b. The rear part 36 b is attached tothe front part of the air cleaner 25. The front and rear parts 36 a and36 b are detachably connected at a dividing position 37. The dividingposition 37 is present behind the rear ends of the pivot plates 6, whichenables the front and rear parts 36 a and 36 b to be easily assembledand maintained.

[0032] The fuel tank 20 has the front end thereof attached to a boss 58at the upper part of the main frames 4 using a bracket 40, and a bolt orthe like. A rear end of the fuel tank 20 is supported on a rear crossmember 43 provided between the upper ends of the pivot plates 6. Thefuel tank 20 has a projection 41 extending downward from it's rear lowerpart. A fuel cock 42 is attached to the bottom of the projection 41.

[0033] The projection 41 is positioned in a space 57 a. The space 57 ais defined behind the cylinder head 27 and cylinder head cover 28, whichextend toward the top of the 4-cycle engine 2, and in front of the rearcross member 43. The projection 41 is as high as the head cover 28 alongthe length of the motorcycle, and overlaps with the upper part of thecarburetor 24 when viewed from the left side of the motorcycle.

[0034] Referring to FIG. 4, the fuel cock 42 is attached with the lowerend thereof extending slightly downward from the lower edges of the mainframes 4, when viewed from the left side of the motorcycle. Further, theprojection 41 overlaps with the main frames 4, and is positioned besidethe carburetor 24 in the widthwise direction of the body frame, asclearly shown in FIG. 3.

[0035] As shown in FIG. 1, the engine 2 has an upper part thereofsupported by the right and left main frames 4. The front part of theengine 2 is supported by the lower part of the down tube 5. The lowerpart of the engine 2 is supported by the intermediate portions of thelower frames 7. Further, the crankcase 29 at the rear part of the engine2 is supported by the right and left pivot plates 6, via the pivot shaft15. As illustrated in FIGS. 2 and 4, the upper part of the engine 2 issupported by the underside of the right and left main frames 4 via ahanger bracket 39 using a support 38 provided at the rear part of thecylinder head 27.

[0036]FIG. 5 illustrates the layout of components near the down tube 5.FIG. 5 shows the arrangement of the radiators 22, down tube 5 and otherperipheral components, viewed from the front part of the motorcycle. Theupper tanks 30 of the left and right radiators 22 are connected by thereturn water hose 31, and communicate with a water jacket outlet nearthe cylinder head cover 28 via a joint tube 31 a.

[0037] The water hose 33 extends from the lower tanks 32 toward thecenter of the motorcycle, and connects to a joint hose 34. The jointhose 34 crosses a rear part of a tapered portion 62 b of the down tube5, and reaches a water pump 49, at the right side of the crankcase, viaa joint 34 a which is positioned at the right side of the joint hose 34.The exhaust pipe 23 passes by the rear part of the tapered portion 62 b,goes obliquely downward to the right side of the motorcycle, and extendsrearward under the right radiator 22.

[0038] Various components are arranged in a space 56 defined under therear cross member 43. FIG. 6 shows the layout of the components, viewedfrom the rear part of the motorcycle. In the space 56, the carburetor 24is positioned near and under the rear cross member 43, and slightly tothe left side of the motorcycle body. The projection 41 is positioned atthe right side of the carburetor 24. The fuel cock 42 is positionedunder the projection 41. A fuel pipe 42 a extends downward from the fuelcock 42 and connects to a float chamber 24 a of the carburetor 24. Thefuel cock 42 is at a level slightly higher than that of the floatchamber 24 a.

[0039] The rear shock absorber 19 is positioned behind the foregoingcomponents and near the center of the motorcycle. The fuel cock 42overlaps with the front part of a reserve tank 19 a, which is juxtaposedwith the rear shock absorber 19. The exhaust pipe 23 extends under thefuel cock 42 and the reserve tank 19 a. The front part of the exhaustpipe 23 extends obliquely rightward from the front part of the cylinderhead 27, then bends toward the center of the motorcycle (see FIG. 5).The exhaust pipe 23 then passes by the inner side of the right pivotplate 6, and under the fuel cock 42 and the reserve tank 19 a asdescribed above. The exhaust pipe 23 then bends slightly to the rightside of the motorcycle, and extends upwards and rearwards. Theconnecting tubes (not shown in FIG. 6) connecting to the carburetor 24and the exhaust pipe 23 are positioned at the opposite sides of the rearshock absorber 19, respectively.

[0040] The structure of the motorcycle body frame 1 will be describedwith reference to FIGS. 7 to 10. The right and left main frames 4 aremade of an aluminum alloy, or the like, which is extruded to have arectangular cross section. The right and left main frames 4 have theirfront ends welded to the head pipe 3, and their rear ends welded to theupper parts of the pivot plates 6.

[0041] The down tube 5 is a square pipe made of an aluminum alloy or thelike, and has its rear lower part tapered by swaging. The rear upperpart of the down tube 5 and the center undersides of the left and rightmain frames 4 are reinforced by a tension pipe 50. The tension pipe 50is substantially horizontal when viewed from the left side of themotorcycle, and is curved to the front part of the motorcycle.

[0042] The tension pipe 50 has its front end coupled to the down tube 5using a gusset 51, and its rear end welded to the main frames 4. A stay52 of the hanger bracket 39 is attached to the welded portion of thetension pipe 50 and the main frames 4. The lower part of the down tube 5is welded to the front parts of the lower frames 7 via a joint 53. Thelower frames 7 are square pipes made of an aluminum alloy or the likeand branched to the left and right (see FIGS. 8 and 9).

[0043]FIG. 10 is a cross section of the down tube 5. The down tube 5 hasfour sides, i.e., a front side 60, a rear side 62, and left and rightsides 63. A rib 61 is formed on the inner center surface of the frontside 60 as an integral part. The rib 61 extends along the length of thedown tube 5. The lower half of the rear side 62 has the downwardlytapered portion 62 b, while an upper surface 62 a of the front half ofthe rear side 62 is straight. Radiator attachments 64, substantially inthe shape of the letter L, are welded to the outer surfaces of the leftand right sides 63. The radiator attachments 64 have weld nuts 65, inorder to bolt the left and right radiators 22.

[0044] As shown in FIG. 7, only the rear side 62 of the down tube 5 hasthe tapered part 62 b, thereby enlarging the space 57 b (shown in FIG.2) defined by the tapered part 62 b, the cylinder head 27 and the frontpart of the cylinder head cover 28. The upper surface 62 a of the rearside 62, the front side 60, and the left and right sides 63 are nottapered, but straight. In other words, the down tube 5 is notsymmetrical due to the presence of the tapered part 62 b, when viewedfrom the left side of the motorcycle.

[0045] The down tube 5 is made as follows. First of all, a square pipehaving a cross section with the rib 61, as the integral part, isextruded and is orthogonally swaged in four directions. This procedureallows the down tube 5 to have a particular side tapered to a desiredlength. The swaging process is well-known, and is effective inoptionally and partially changing a thickness of one side of the downtube 5, so that the rib 61 can be easily formed.

[0046] The pivot plates 6 are made by a process such as casting orforging an aluminum alloy. The pivot plates 6 are in the shape of aplate, and have upper ends 54 extending higher than the rear ends of themain frames 4. The upper ends 54 are curved inward (see FIGS. 8 and 9),and have recesses on their curved surfaces. The opposite ends of therear cross member 43 are fitted into these recesses and are weldedtherein. Pivot receptacles 55 are formed under the centers of the pivotplates 6, thereby receiving the opposite ends of the pivot shaft 15.

[0047] The rear cross member 43 is made by a process such as casting orforging an aluminum alloy or the like. The rear cross member 43 ispreferably hollow. The rear cross member 43 receives the rear end 45 ofthe fuel tank 20 on the upper surface 44 thereof. A center of the rearcross member 43 includes a forked shock absorber bracket 46 as anintegral part. The shock absorber bracket 46 extends rearward, andmovably supports an upper end of the rear shock absorber 19. The rearshock absorber bracket 46 is slightly offset from the center C of themotorcycle, and is positioned in order to minimize the offset. The shockabsorber bracket 46 has on its upper part an opening 46 a for mountingthe seat rails 8 (see FIG. 4).

[0048] As illustrated in FIG. 6, the space 56, defined under the rearcross member 43 and between the left and right pivot plates 6 and thepivot shaft 15, is very large. The space 56 houses the rear shockabsorber 19, exhaust pipe 23 and connecting tube 36. As illustrated inFIG. 8, the large space 57 in front of the rear cross member 43 extendsabove the tension pipe 50 and behind the head pipe 3, and houses thefuel tank 20 therein. A rear cylinder space 57 a is present at the rearpart of the space 57, i.e. behind the cylinder head cover 28 of theengine 2 (see FIG. 3).

[0049]FIGS. 8 and 9 illustrate a boss 58 for attaching the bracket 40integrally with the head pipe 3. A cross member 59 extends from the rearpart of the head pipe 3, as an integral part. The cross member 59 joinsthe left and right main frames 4. As illustrated in FIG. 7, a stay 53 ais provided at the joint 53 in order to support the engine 2. Also,stays 7 a are provided at the lower frames 7 in order to support theengine 2.

[0050] Now, an example of an operation of the present invention will bedescribed. Referring to FIGS. 2 and 4, the downward projection 41provided on the bottom towards the rear of the fuel tank 20 is effectivein increasing the capacity of the fuel tank 20. The fuel tank 20 canhave a relatively larger capacity without becoming taller. This enablesthe riding position and seat 21 to be secured relatively near the frontpart of the motorcycle body. This reduces variations of the center ofgravity caused by an amount of fuel remaining in the fuel tank 20,and/or changes of a riding position of the rider, and so on.

[0051] As shown in FIGS. 3 and 6, the projection 41 and carburetor 24are juxtaposed across the motorcycle body so that the space 57 a infront of the carburetor 24 can be effectively used. Further, the space57 a is also present behind the cylinder head 27 and cylinder head cover28, and in front of the rear cross member 43, and is effective inpreventing the positions of the cylinder head 27 and cylinder head cover28 of the 4-cycle engine 2 from being raised.

[0052] The fuel cock 42 is attached under the projection 41, i.e. thefuel cock 42 is positioned beside the carburetor 24. The arrangementeffectively uses the space 57 a, and improves layout tolerance for thefuel cock 42. The fuel cock 42 is positioned at a low level near thefloat chamber 24 a, which is effective in reducing a length of a fuelpipe 42 a extending from the fuel cock 42 to the carburetor 24 and infacilitating the installation of the fuel pipe 42 a. Further, since thefuel cock 42 is present at the bottom of the fuel tank 20, little airwill be sucked, even if the fuel level fluctuates when there is a smallamount of fuel in the fuel tank 20.

[0053] As illustrated in FIG. 6, the exhaust pipe 23 is installed in thespace under the fuel cock 42 and the reserve tank 19 a, whichfacilitates the installation of the exhaust pipe 23, and promoteseffective use of the available space.

[0054] Still further, the fuel cock 42 has its bottom positioned nearthe lower edges of the main frames 4. This enables the fuel cock 42 tobe at a manually accessible position even if the main frames 4 have arectangular cross section. In addition, the fuel cock 42 can bemanipulated from the right side of the motorcycle body, which isopposite to the left side where the carburetor 24 is positioned.Therefore, the fuel cock 42 can be maintained without being affected bythe carburetor 24.

[0055] The invention being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

We claim:
 1. A motorcycle comprising: an engine; a fuel tank mountedabove said engine; a fuel cock attached to said fuel tank; and acarburetor communicating fuel from said fuel cock to said engine,wherein said fuel cock and said carburetor are at least partiallyoverlapped when viewed from a direction taken perpendicular to a normaltravel direction of said motorcycle.
 2. The motorcycle according toclaim 1 , wherein said carburetor is located on a left side of saidmotorcycle, and said fuel cock is located on a right side of saidmotorcycle, when facing to a normal travel direction of said motorcycle.3. The motorcycle according to claim 1 , wherein said fuel cock islocated below a center of gravity of said motorcycle.
 4. The motorcycleaccording to claim 1 , wherein said fuel tank includes a downwardprojecting portion, and wherein said fuel cock is attached to, andextends downward from, said downward projecting portion.
 5. Themotorcycle according to claim 4 , wherein said engine includes acylinder head cover, and wherein said downward projecting portion islocated behind said cylinder head cover, in reference to a normal traveldirection of said motorcycle.
 6. The motorcycle according to claim 1 ,further comprising: a seat, and wherein said fuel tank extends undersaid seat.
 7. The motorcycle according to claim 1 , wherein said fuelcock is present at a lowest portion of said fuel tank.
 8. The motorcycleaccording to claim 7 , wherein said carburetor includes a float chamber,and wherein said fuel cock is at a level slightly higher than said floatchamber of said carburetor.
 9. A motorcycle comprising: an engine; apair of right and left main frames extending above said engine inlengthwise direction of the motorcycle; a fuel tank mounted above saidengine, and between said left and right main frames, said fuel tankincluding a downward extending portion at a rear portion of said fueltank, downstream in reference to a normal travel direction of saidmotorcycle; and a fuel cock attached to said downward extending portionof said fuel tank, wherein said fuel cock is manually accessible frombeneath one of said right and left main frames.
 10. The motorcycleaccording to claim 9 , wherein said fuel cock extends at least partiallybelow said left main frame.
 11. The motorcycle according to claim 9 ,further comprising: a rear cross member extending across saidmotorcycle.
 12. The motorcycle according to claim 11 , wherein saidengine includes a cylinder head cover, and wherein said downwardprojecting portion is located behind said cylinder head cover and infront of said rear cross member, in reference to a normal traveldirection of said motorcycle.
 13. The motorcycle according to claim 11 ,wherein said fuel tank is supported on said rear cross member.
 14. Themotorcycle according to claim 11 , further comprising: a right pivotplate connected to said right main frame; and a left pivot plateconnected to said left main frame, wherein said rear cross memberconnects said right pivot plate to said left pivot plate.
 15. Themotorcycle according to claim 14 , wherein said engine includes acylinder head cover, and wherein said downward projecting portion islocated behind said cylinder head cover and in front of said rear crossmember, in reference to a normal travel direction of said motorcycle.16. The motorcycle according to claim 9 , further comprising: an exhaustpipe of said engine extending under said fuel cock.
 17. The motorcycleaccording to claim 9 , wherein said left and right main frames haverectangular cross sections.
 18. The motorcycle according to claim 9 ,wherein said fuel cock is located at a lowest portion of said fuel tank,and below a center of gravity of said motorcycle.
 19. The motorcycleaccording to claim 9 , further comprising: a carburetor communicatingfuel from said fuel cock to said engine, wherein said fuel cock and saidcarburetor are at least partially overlapped when viewed from adirection taken perpendicular to a normal travel direction of saidmotorcycle.
 20. The motorcycle according to claim 19 , wherein saidcarburetor includes a float chamber, and wherein said fuel cock is at alevel slightly higher than said float chamber of said carburetor.